Stabilization of fats and oils with 2, 5-dihydroxyphenyl dimethyl carbinol and related antioxidants



Patented May 19, 1953 STABIL'EZATION OF FATS AND- OILS WITH 2,5-DIHYDROXYPHENYL DIMETHYL CAR- BINOL AND RELATED ANTIOXIDANTS Alan Bell and Donald J. Shields, Kingsport, Tenn, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application April 23, 1952,

Serial N0. 283,972

19 Claims. (Cl. 260-398.5)

This invention relates to the stabilization of fats, oils and other organic materials subject to deterioration employing compounds as antioxidants which are 2,5-dihydroxyphenyl (or benzyl) dialkyl (or arylalkyl) carbinols.

U. S. 2,104,084 discloses the stabilization of fats and oils with compounds which are in some instances homologs of those employed in the instant invention. However, these prior art compounds do not contain tertiary hydroxy radicals nor do they include compounds containing three hydroxy radicals, both of which characteristics contribute to the superior properties of the antioxidants of this invention.

One of the compounds disclosed as an antioxidant herein is believed to be known in the prior art only as a heading in Beilstein, volume VI, page 1124, cf. Klages, Berichte, 37,3996 who is said to have prepared 2,5-dimethoxyphenyl dimethyl carbinol which is described as a thick oil having a high boiling'point.

It is an object of our invention to provide compounds which are believed to be novel and which possess improved properties which are especially useful in the stabilization of fats and oils. Another object is to provide antioxidant compositions containing the principal antioxidants of this invention admixed with .a synergist. A further object of our invention is to provide antioxidant compositions of this nature dissolved in an inert organic solvent. An

by weight of an antioxidant selected from those having the following-"formulas:

w H 1E2 1 f-Q 0H OH H a OH 2 l a rec?- OH H g wherein R1 represents a substituent selected from those consisting of an alkyl group con- 'taining from 1 to 4 carbon atoms and an 'aryl group of the benzene series containing from 6 to 9 carbon atoms, R2 represents an alkyl group containing from 1 to 4 carbon atoms, and R3 represents a substituent selected from those consisting of R1'as defined above and a hydrogen atom.

Examples of such antioxidants included in the above formulas are 2,5-dihydroxyphenyl dimethyl carbinol, 2,5-dihydroxyphenyl diethyl carbinol, 2,5-dihydroxybenzyl dimethyl carbinol, 2,5-dihydroxybenzy1 methyl ethyl carbinol, 2,5- dihydroxyphenyl methyl phenyl carbinol, 2,5- dihydroxyphenyl ethyl p-tolyl carbinol, 2,5-dihydroxybenzyl propylxylyl carbinol, etc.

A preferred compound of the above group of antioxidants is 2,5-dihydroxyphenyl dimethyl carbinol. This compound can also be called 1-hydroxisopropylhydroquinone. It has been found that the employment of the l-hydroxyisopropyl group on the hydroquinone nucleus results in the existence of a compound with unexpectedly advantageous antioxidant properties. As can be seen from the table which is presented hereinafter, this compound is more potent as an antioxidant than isopropyl hydroquinone. It might be theorized that this novel antioxidant is of especial value because it may be converted in situ when heated in a fat or oil being stabilized so as to form isopropenyl hydroquinone which is an exceedingly useful and potent antioxidant as described and claimed in a copending application filed on May 31, 1951, by Bell, Knowles and Tholstrup, Serial No. 229,281. In conjunction with this theoretical consideration, it would appear that the compound 2,5 -dihydroxybenzyl dimethyl carbinol would also be a valuable antioxidant inasmuch as it would appear preferable that the hydroxy group be in a position alpha or beta to the benzene ring whereby an olefinic double bond in conjugated relation to the benzene ring might be formed in situ when the antioxidant I droxy-5-methoxy-phenyl dimethyl carbinol has very little effectiveness as an antioxidant, whereas the theoretical considerations presented above indicate that the compound 2-isopropenyli-methoxyphenol disclosed on page 3 of a copending application filed May 31, 1951, by Bell, Knowles and Tholstrup, Serial No. 229,282, would appear to be a valuable antioxidant if it could be formed in situ. This discussion makes it evident that it is exceedingly diificult to make predictions regarding the antioxidant efficacy of compounds such as those covered by the instant invention. Consequently, itcan be stated that the compounds covered by this invention which can be employed as valuable antioxidants are restricted to those wherein the. hydroxy' group is tertiary and is attached to thealpha or beta carbon atom to the benzene ring.

In regard to the compound 2-hydroxy-5- methoxyphenyl dimethyl carbinol which was re-" ferred to above, this compound can be prepared by reacting the methyl ester of. 2-hydroxy-5- methoxybenzoic acid with methyl magnesium iodide.

The compounds of this. invention which have been described above are quite useful as antioxidants for fats and oilsas has been indicated. When so employed, fractions of'a percent of such compounds can be incorporated into such materials as lard, cottonseed oil, peanut oil, etc., by admixing the antioxidant with thefats and oils whereby a solution of the antioxidant in the substrate is obtained. Alternatively, the antioxidant can be blended with suitable solvents to form an antioxidant solution. Examples of such solvents include glycerin and propylene glycol. Such antioxidant solutions can be more readily dis solved in the fat or oil to be stabilized with less necessity for prolonged mixing of the fat or oil with the undissolved anti-oxidant. Similarly, synergists can be admixed with. the fats or oils along with the dry antioxidant compounds of this invention or, in orderto facilitate the incorporation of the antioxidant and synergist into the fat or oil, they canwbothbe dissolved in such solvents as'propylene glycol, glycerin, hexane, etc, or other similar solvents which, areinert insofar as concerns both the antioxidant and/or the synergist-components in the ultimately prepared stabilized fat or. oil. Examples of synergists whichcan be employed include 'citricacid, tartaric acid, phosphoric acid, ascorbicacid, etc. In addition to the employment, of a single antioxidant asdescribed hereinbefore, mixtures of two or more such antioxidants together with two or more synergists can beemployed. Moreover, otherantioxidants which are known in the art can be added for their supplemental efiects if such be desired.

In addition to the'fats and oils mentioned above which can be stabilized by the antioxidants of this invention, other representative fats and oilsinclude linseed oil, menhaden oil,-cod liver oil, castor oil, olive oil, rape seed oil, cocoanut oil, palm oil, corn oil, sesameaoil, peanutoil, babassu oil, butter fat, lard, beef tallow, etc., as well as hydrogenated oils-and fats prepared from any of the foregoing. Further-more. various other oils and fats may be similarly treated within the- A preferred procedure for preparingcompounds of the type. disclosed hereinabove as antioxidants;

.4 is set forth in the examples which are given below. The prior art disclosure by Klages indicates that 2,5-dimethoxypheny1 dimethyl carbinol can be prepared by the reaction of methyl magnesium iodide with 2,5 dimethoxyacetophencne. The product obtained by Klages is said to be a thick oil having a boiling point at 16 mm. Hg of 138-1=i1 C. It is believed that this product was actually an impure form of 2,5-dimethoxyphenyl dimethyl carbinol. Such a product would not be usefulias an antioxidant since it contains no free phenolic hydroxyl radical.

The antioxidants of this invention can be prepared-by a procedure which can be employed to prepare 2,5rdihydroxyphenyl dimethyl carbinol aswell as the other compounds related thereto. This procedure can be illustrated by the following. schematic series of reactions:

The following example illustrates the preparation of 2,5-dihydroxyphenyldimethyl carbinol:

Example 1 .2,5-dihydroxyphenyl dimethyl carbinol A suspension of 148' partsof 2,5-dibenzyloxyacetophenone-in ethyl ether was added with stirring and cooling to anethereal solution of methyl magnesium iodide. The latter "solution was prepared from .1315 parts of magnesium and 80.25 parts of methyl iodide. As the addition prograssed a creamy precipitate appeared. The mixture was stirred for several hours and allowed to stand overnight. The mixture was then poured over a mixture of ice and excess ammonium chloride. The ether layer was separated, dried over calcium chloride, and the ether distilled to leave a residue which was recrystallized from hexanebenzene; The. resulting dibenzyl ether Which melted at 77 C. was obtained in a yield of 89.6 percent. (137 parts)-.

Ten parts of the dibenzyl" ether was dissolved in 125:parts of ethanol and reduced at'20-30 C. with hydrogen at 40 pounds per square inch (p. s. i.) in the presenceofi one part. of 5-percent palladium on charcoal. The hydrogenolysis was stopped when the theoreticalamount of hydrogen had been absorbed. Thecatalyst was removed by filtration and the ethanol was removed under nitrogen in vacuo. The resulting residue solidilied and was recrystallized from hexane to give 3.6 parts percent) of 2,5-dihydroxyphenyl diimethyl carbinol which melted at 133 C.

The product obtained in accordance with the preceding example canwbe' employed as an antioxidant as illustrated in the table presented below wherein a number of examples are set forth of antioxidants described hereinbefore.

In investigating the properties of the 2,5-dihydroxyphenyl dimethyl canbinol, an attempt was made to dehydrate this compound by refluxing in benzene in the presence of a trace of iodine. Wa-

ter was split out easily but the expected isopropenyl hydroquinone was not isolated in an appreciable quantity. The product obtained was a solid which melted at 193195 C. and which was analyzed and apparently had the formula (C9H10O 2) 1!.- It appears that the product obtained 2 was probably the dimer.

In regard to this dehydration product of 2,5- dihydroxyphenyl dimethyl carbinol, a similar dimeric product was also obtained as one of the products produced in accordance with the following precedure:

Example 2.--Dimer from 2,5-dihydroacyphenyl dimethyl carbinol 115 parts of 2,5-dibenzyloxyphenyl dimethyl carbinol was dissolved in ethanol and treated at 20-30 C. with hydrogen at 40 p. s. i. (pounds per square inch) in the presence of 5 percent palladium on charcoal. Evaporation of the sol- 40 vent and trituration with hexane gave 50 grams (90%) of a product. The product contained 10 percent of 2,5-dihydroxyphenyl dimethyl carbinol and the remainder was identical with the dimer obtained above by dehydrating 2;5-dihydroxyphenyl dimethyl carbinol. This product on recrystallization from benzene melted at 192- 193 C. This product had antioxidant properties as indicated by the table below. Apparently debenzylation, dehydration, and dimerization 00- ture of this dimer indicates that it may be as follows:

' OH OH CH3 CH 5 e I -CH=C I OH OH Infrared data tend to substantiate the above structure.

In addition to' the preparation of the antioxidant compounds described above, the various procedures we have employed have resulted in the preparation of somewhat analogous compounds such as: 2-hydroa:y-5-methoa:yphenyl dimethyl carbinol The compound 2-benzyloxy-5-methoxyacetophenone was reacted with'methyl magnesium iodide followed by debenzylation with hydrogen and palladium as described in Example 1 above. The product obtained was 2-hydroxy-5-methoxypheny dlimethyl carbinol which had a melting point at 98-99 C. This product retained the methoxy group on the benzene ring, viz. the methoxy group was not demethylated.

The compound just described was also prepared by reacting the methyl ester of Z-hydroxy- '5-methoxybenzoic acid with methyl magnesium iodide using the procedure described above in Example 1 whereby an 86.5% yield was obtained of 2-hydroxy-5-methoxyphenyl dimethyl carbinol. This product melted at 98-99 C. The theoretical empirical formula is C1OH1403 (65.93% carbon and 7,69% hydrogen). Upon analysis it was found that the compound obtained contained 65.94% carbon and 7.92% hydrogenon one analysis and 66.25% carbon and 7.88% hydrogen on another analysis.

The above results clearly indicate that the compound described in the prior art by Klages is not the same as the compound which is the preferred antioxidant of this invention.

Inasmuch as it is well known in theart to employ antioxidants in the stabilization of fats and oils, it is not believed necessary to give numerous specific examples of how the antioxidants of this invention are blended with fats or oils nor the specific proportions which can be employed in the many possible examples which would come within the scope of the description given hereinabove. The following tabulation and data is presented in order to show the properties of an antioxidant of this invention and how its properties compare with other antioxidants including those known in the prior art:

COMPARATIVE ANTIOXIDANT PROPERTIES Antioxidant Lard Cottonseed Oil Peanut Oil Synergist- Citric acid, 20 20 20 70 100 Compound Percent Percent AOM P. F. .AOM AOM P. F. AOM AOM AOM P. F AOM A. Control (I) g 3.5 1.0 B. 2,5-dihydroxyphenyl dimethyl carbinol 8; g 38:8 522.? C. Dimericform (cf.Examp1e .01 0 40.0 6.2

v 01 0 34. 0 9. 7 22. 0 2. 7 D. tert.-butyl hydroquinone 005 38. 5 11.0, 22. 0 2. 7 .02 0 67.0 19.1 30.0 3.8 E. Isopropy1-hydroqujn0ne 8 ""5 6. "55.

2 5 33. F. Propenyl hydroqulnone 005 77 0 22 0 24 0 33 5 2 9 8 egg 3010 4910 4.3 16. 0 25. O 2. 2 G. Dnsopropenyl hydro ul- Demeter-P10129381 13% 3. it?) 13:3- tiig it? it 1 This test conducted in lard having a control ADM value of 6.5.

ata; pr sent dshare s as d: a t sts. conducted under equivalent conditions employing.

similar samples in each instance-of cottonseed oil, peanut oil, and lard, except as indicated. The AOM figures a reinhours; the symbol P. F. represents the protection factor which is the ratio of the AOlE/I value of the stabilized substrate to that of the control which contains no antioxidant. The numbers beneath the name of the at on n a e he erox de al es 9v h ch he sample was brought in order to determinethq,

M- al e.- T procedu m y d u e h QM. a i e. xy e method-l is lknow n the an o id nt a a d a be ex l ined n t i Y mined by iod-ometric titration, expressing results as milliequivalents per kilogramof'fat or oil. Experience has shown that initial rancidity in lard corresponds closely to a peroxidey'alue of and to '70 in oils such as cottonseed oil and peanut oil. The. latter value has not been firmly estab: lished but is useful for comparative purposes, A control containing no additives was run simultaneously with the test compound to. determine the. induction period ofthe .unstabilized material.

The final results are. expressed as. the number of hours required for rancidity. to develop; 1. e., anAOM value of 40 for a sample of lard means that 40. hr; was required to form twenty milliequivalents of peroxide per kilogram of the lard.

A perusal of this-data indicates that 2,5.-dihydroxyphenyl dimethyl carbinol is a superior. antioxidant for fats and oils, particularly lard. Of the data presented, only propenyl hydroquinone is superior in lard; this latter compound is disclosed for the first time. as an antioxidant for fats and oils in the copendi-ng. application referred to above.

We claim:

1. Stabilized fats and oils containing from about 0.001% to about 1.0% by wfeight of an antioxidant selected from those having the following formulas:

OH R:

and

fiabina d ta nd s a d fined nq a m, wherein the" antioxidant is 2,5-dihydroxyphenyl methyl ethyl carbinol.

'4. Stabilized'fatsand oils as defined in claim 1 wherein the antioxidant is 2,5-dihydroxyphenyl diethyl. carbinol.

5. Stabilizedfats and oilsas defined in claim 1, wherein theantioxidant is 2,5-dihydroxybenzyl dimethyl carbinol.

6. Stabilized'fats and oils as defined in claim 1 wherein the antioxidant is 2,5-dihydroxybenzyl methyl ethyl carbinol.

'7. A process for stabilizing fats and oils which comprises admixing therewith from about 0.001%

lected from those having the following formulas:

OH 2 I and OH 2 a I wherein R1 represents a substituent selected from those consisting of an alkyl group containing from 1 to 4 carbon atoms and an aryl group of the benzene series containing from 6 to 9 carbon atoms, R2 represents an. alkyl group con-.- taining from 1 to 4 carbon atoms, and R3 represents a substituent selected from those consisting of R1 as defined above and a hydrogen atom.

8. A process for stabilizing fats and oils as defined in claim 7 wherein the antioxidant is 2,5- dihydroxyphenyl dimethyl carbinol.

9. A process for stabilizing fats and oils as defined in claim 7 wherein the antioxidant is 2,5- di-hydroxyphenyl methyl ethyl carbinol.

10. A process, for stabilizing fats and oils as defined in claim '7' wherein the antioxidant is 2,5-dihydroxyphenyl diethyl carbinol.

11. A process for stabilizing fats and oils as defined in claim 7 wherein the antioxidant is 2,5-dihydroxybenzyl dimethyl carbinol.

12. A process for stabilizing fats and oils defined in claim 7 wherein the antioxidant 2,5-dihydroxybenzyl methyl ethyl carbinol.

1? Stabilized fats and oils containing from about 0.0005% to about 0.05% by weight of a synergistic 'acid selected from the group consisting of citric acid, tartaric acid,- phosphoric acid, ascorbic acid, alanine and cysteine and from about 0.001%to about 0.1 by weight of an antioxidant selected from those having the following is is formulas:

OH I 3.1-?

OH and OH 2 l a I l C 0E Ill wherein R1 represents a substituent selected from those consisting of an allgyl groupcontaining from 1 to 4 carbon atoms and an aryl group of the benzene series containing'from 6 to 9 carbon OH 2 I and wherein R1 represents a substituent selected from those consisting of an alkyl group containing from 1 to 4 carbon atoms and an aryl group of the benzene series containing from 6 to 9 carbon atoms, R2 represents an alkyl group containing from 1 to 4 carbon atoms, and R3 represents a substituent selected from those consisting of R1 as defined above and a hydrogen atom.

15. Stabilized fats and oils as defined in claim 14 wherein the antioxidant is 2,5-dihydroxyphenyl dimethyl carbinol.

16. Stabilized fats and oils as defined in claim 14 wherein the antioxidant is 2,5-dihydroxyphenyl methyl ethyl carbinol.

1'7. Stabilized fats and oils as defined in claim 14 wherein the antioxidant is 2,5-dihydroxyphenyl diethyl carbinol.

18. Stabilized fats and oils as defined in claim 14 wherein the antioxidant is 2,5-dihydroxybenzyl dimethyl carbinol.

19. Stabilized fats and oils as defined in claim 14 wherein the antioxidant is 2,5-dihydroxybenzyl methyl ethyl carbinol.

ALAN BELL. DONALD J. SHIELDS.

No references cited. 

1. STABILIZED FATS AND OILS CONTAINING FROM ABOUT 0.001% TO ABOUT 1.0% BY WEIGHT OF AN ANTIOXIDANT SELECTED FROM THOSE HAVING THE FOLLOWING FORMULAS: 